1. Field of the Invention
Apparatuses and methods consistent with exemplary embodiments relate to an image forming apparatus and a color-tone density (CTD) controlling method thereof, and more particularly, to a multi-path type image forming apparatus and a CTD controlling method thereof.
2. Description of the Related Art
Image forming apparatuses are apparatuses which print printing data generated in a terminal apparatus, such as a computer, on a recording paper. As an example of the image forming apparatuses that perform such functions, there are copiers, scanners, facsimiles, or multiple function peripherals (MFPs) which multiply implement functions thereof through one apparatus.
In recent years, laser image forming apparatuses with remarkable effects in terms of printing quality, printing speed, noise in printing, and the like as compared with dot image forming apparatuses or inkjet image forming apparatuses which have mainly been used in the related art have been used increasingly. The laser image forming apparatuses are apparatuses using the principle which coats a toner to an organic photo conductor (OPC) using laser light ray modulated into a picture signal, transfers the toner coated on the OPC to a printing paper, and fixes the toner on the printing paper with high heat and pressure.
In particular, color laser image forming apparatuses which also implement color using a laser system have been increasingly used in recent years. In general, the color laser image forming apparatuses represent a color image using four color toners of cyan (C), magenta (M), yellow (Y), and black (K).
In the color laser image forming apparatuses, there are a single-path system including four laser scanning units and four OPCs and a multi-path system including one laser scanning unit and one OPC.
The time required in color printing and the time required in black and white printing are the same in the single-path system. Therefore, the single-path system is mainly used in high-speed color laser image forming apparatuses. However, since the high-speed color image forming apparatuses include the four laser scanning units and the four OPCs, the production cost becomes expensive. Thus, color laser image forming apparatuses which operate in a relatively low-speed range employ the multi-path system which includes one OPC and one laser scanning unit and repeatedly performs a writing operation, a developing operation, and a transferring operation for each color to form a color toner image on an intermediate transfer belt, and transfers and fixes the color toner image to a paper.
The CTD of an image formed by the color laser image forming apparatuses is changed due to various factors such as change in an environment such as a temperature or a humidity, temporal change in consumables including a developer, or change in voltages related to the development. To uniformly maintain the CTD of the image, it is necessary to measure the CTD of the image periodically or at a specific point of time and appropriately control development variables according to the measured result.
The method of controlling a CTD of an image in the prior multi-path type color laser image forming apparatus will be described. The CTD of a test patch formed on an OPC or an intermediate transfer belt is measured using a CTD sensor. The measuring operation for each developer is repeatedly performed to repeatedly measure the CTD and then final development variables are determined.
However, when the test patch is developed on the OPC in the related art, the test patches for CMYK are developed in order of the Y, M, C and K test patches. That is, the test patches are developed as shown in FIG. 1. This is because the development operation which is performed in order of the Y, M, C, and K developers in a color printing job is applied to the test patch development operation.
When the test patches are developed in order of Y, M, C, and K developers as in the related art, an unnecessary operation is caused when the test patch is developed in association with the configuration of the image forming apparatus, and it takes a long time to measure the CTD of the test patch.